1. Field of the Invention
The present invention relates to an integrated semiconductor laser device and a method of fabricating the same, and more particularly, it relates to an integrated semiconductor laser device comprising a plurality of semiconductor laser elements and a method of fabricating the same.
2. Description of the Background Art
An integrated semiconductor laser device prepared by integrating a plurality of semiconductor laser elements in the direction of stacking of semiconductor layers is known in general, as disclosed in Japanese Patent Laying-Open No. 2002-299739, for example.
FIG. 133 is a perspective view showing the structure of a conventional integrated semiconductor laser device. Referring to FIG. 133, a first semiconductor laser element 410 and a second semiconductor laser element 420 are integrated with each other in the direction (vertical direction Z) of stacking of semiconductor layers in the conventional integrated semiconductor laser device.
A ridge portion 412 and a recess portion 413 are formed on a semiconductor element layer 411 constituting the first semiconductor laser element 410. The ridge portion 412 and the recess portion 413 are arranged at a prescribed interval in the horizontal direction (direction X). A peripheral region of the ridge portion 412 of the semiconductor element layer 411 forms an emission region 414 of the first semiconductor laser element 410. Another ridge portion 422 and another recess portion 423 are formed on another semiconductor element layer 421 constituting the second semiconductor laser element 420. The ridge portion 422 and the recess portion 423 are also arranged at a prescribed interval in the direction X. A peripheral region of the ridge portion 422 of the semiconductor element layer 421 forms an emission region 424 of the second semiconductor laser element 420.
The first and second semiconductor laser elements 410 and 420 are bonded to each other through bonding layers 415 and 425. More specifically, the first and second semiconductor laser elements 410 and 420 are so bonded to each other that the ridge portion 412 of the first semiconductor laser element 410 and the recess portion 423 of the second semiconductor laser element 420 positionally coincide with each other while the ridge portion 422 of the second semiconductor laser element 420 and the recess portion 413 of the first semiconductor laser element 410 also positionally coincide with each other.
In the conventional integrated semiconductor laser device shown in FIG. 133, however, the ridge portion 412 (ridge portion 422) of the first semiconductor laser element 410 (second semiconductor laser element 420) is not fitted in the recess portion 423 (recess portion 413) of the second semiconductor laser element 420 (first semiconductor laser element 410). When the first and second semiconductor laser elements 410 and 420 are bonded to each other, therefore, it is disadvantageously difficult to inhibit the first and second semiconductor laser elements 410 and 420 from horizontally moving in the directions X and Y. Thus, the first and second semiconductor laser elements 410 and 420 are disadvantageously bonded to each other while cleavage directions thereof do not coincide with each other. Consequently, cleavability for simultaneously cleaving the first and second semiconductor laser elements 410 and 420 is reduced to disadvantageously deteriorate the properties of a laser beam emitted from a cleavage plane (light emission plane).
In the conventional integrated semiconductor laser device shown in FIG. 133, further, the emission regions 414 and 424 of the first and second semiconductor laser elements 410 and 420 are arranged at prescribed intervals in the horizontal direction X as well as in the direction Z of stacking of the semiconductor layers. In other words, the emission regions 414 and 424 of the first and second semiconductor laser elements 410 and 420 misregister from each other in two directions, i.e., the horizontal direction X and the direction Z of stacking of the semiconductor layers. Therefore, the intervals between the emission regions 414 and 424 are disadvantageously increased as compared with a case where the emission regions 414 and 424 misregister from each other only in the direction X or Z. If the intervals between the emission regions 414 and 424 are increased, a beam emitted from either the emission region 424 or the emission region 414 may be incident upon a region displaced from a prescribed region of an optical system formed by a lens and a mirror in a case of introducing a beam emitted from the integrated semiconductor laser device into the optical system also when optical axes are so adjusted as to introduce a beam emitted from either the emission region 414 or the emission region 424 into the prescribed region of the optical system. Consequently, it is so difficult to adjust the optical axis of the beam emitted from the integrated semiconductor laser device with respect to the optical system that the cost for the optical axis adjustment is disadvantageously increased.